Service Tax Registration

Would like to have 2 clarification while filling Service Tax Registration Form 1. In case of a construction company which has 2 -3 sites, can we have centralized registration (the company has opted for abatement of 75% - So no input credit will be available). The issue is how to communicate to dept about our running site since AO may reach our site and raise question that site is not a registered premises. 2. While doing registration what category we should enter - shall just service provider do or we need to add something more.. Kindly guide ... Regards Juhi